[Bug tree-optimization/60770] disappearing clobbers

["glisse at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60770

--- Comment #6 from Marc Glisse <glisse at gcc dot gnu.org> ---
(In reply to Marc Glisse from comment #5)
> The problem is during the TODO, in execute_update_addresses_taken, which
> finds out that q does not need its address taken anymore, and
> 
>                 /* For var ={v} {CLOBBER}; where var lost
>                    TREE_ADDRESSABLE just remove the stmt.  */

Added by Jakub for PR 50317.

> Maybe it could instead create an uninitialized ssa_name for var.

In r190200, Richard added to rewrite_stmt:

            /* If we rewrite a DECL into SSA form then drop its
               clobber stmts and replace uses with a new default def.  */

rewrite_update_stmt doesn't do the same, but I think it would make sense if it
did. I am having some difficulty finding the right place to do it so the
bookkeeping works properly (the clobber has a vdef, so there are vuses to
update at least), so I can't easily test the impact it would have.